Can alarm system sensors serve double duty?

Homematic has sensors, PIRs and a siren etc for an alarm. You can use it standalone, with openHAB or together.

There are others too.

Thanks @Saracen… I was leaning toward using something like ADT, DSC, Simplisafe etc. for the alarm system. Would you happen to know if OH can use any of these systems sensors? Appreciate it.

No idea,sorry. I doubt it though.
‘Proper’ security systems tend to be, by their very nature, locked down against any external access.


Yes - I have done this with a Namco security system. Sensors are hardwired to a bus on the computer unit. What I did was measure the voltage on each sensor terminal on the main computer - it changes depending on the status of the sensor (door open/closed, motion detector tripped, etc.) - using a digital voltmeter. I then used a simple voltage divider (two resistors of high resistance wired in series. One end is connected to the alarm system sensor terminal. The other end is grounded. Make sure you use high resistance values to minimize the voltage drop on the alarm terminal). The voltage divider drops the voltage to a level that an Arduino can read on its anaog input pins (< 5 volts, as my alarm system bus runs at ca. 9-10 volts). I then wrote an Arduino sketch to read the voltage on the analog inputs and report the value of the corresponding sensor via MQTT to Openhab. It works flawlessly, and you can write rules to take action based on the sensor status.

I believe most commercial alarm panels operate using the same principle. I suggest you do this only if you have some experience with electronics.

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Yes, it’s possible.
I used to use battery powered Zwave sensors, but they drove me crazy.
I’v just installed a DSC alarm system with a PIR in every room, I interface it to OpenHab via an Envisalink 4 card.
I use it to control lights in several rooms, a couple of actions based on armed/disarmed status & send SMS out in case of Intrusion, Panic & Fire alarms.

I used to have ADT (came with the house). Then I unsubscribed from their service and I am now using EyezOn. I have the Vista 20P Hooked up onto an AlarmDecoder device. This device interfaces with the Alarm panel using a good ole RS232, so anything happening to the alarm, gets fed to my OH through the AlarmDecoder module. There is an AlarmDecoder Binding for OH that I have been using for a long time now. Any sensor you have hooked up on the Alarm gets fed to the binding using the Alarm Decoder Protocol, which means you can do anything with the sensors too!

Also, with this merged changes ( ) you can also determine what your Alarm is sending to the monitoring company.

I use all my Vista20P (alarm) sensors with my OH.

You can see my setup here and here

I do exactly this with my DSC alarm and the Envisalink add-on board.

one big reminder: openHAB is not intended for use of vital and/or security appliances.
of Course you’ll get some updates on sensors and stuff - but neither openHAB nor the “normal PIR sensors” are certified for that use in critical environments.

That being said: If you find an alarm system, which has the means of an API and/or some binary outputs or whatever, you can of course use that one with your openHAB. My standard example is heating, I do have a heating controlling unit, which I can access via RS232 - I read out all sensors of the Installation (some 60+ sensors on temperature, valve Status, …), but I don’t interfere with the heating’s own logic. I only tell the heating “Vacation” or “Set temperature” - and I use the heatings internal - certified - logic. That way I don’t come home to a frozen house, if I accidently saved a misconfiguration in another rule, which broke the whole OH2.

Long Story short:
Try to use certified appliances and devices, where it’s vital and crucial - if those grant you access, you’re free to use it!


:+1: Common sense comes into mind.

“Some” examples of what I do with OH + Alarm:

  • Presence detection + Auto Arm
  • Auto Arm @ specific times of night
  • Added NFC/RFID + ESP to disarm
  • Auto pan indoor camera to where PIR motion is triggered, then take a snapshot

I have a Leviton Omni security system and use the OmniLink binding to access it. It works great and I use OH to Arm / Disarm and turn on and off lights with the door sensors.

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Thanks for the reply @noemark1. I’m not experienced with electronics so this method is probably one I won’t be able to do. Thanks for taking time to reply.

Just read all of your replies. Really appreciate it! Long story short, budget is tight and it may be more cost effective for me to just let the alarm system stand alone from a sensor standpoint and use zwave sensors for PIR and open/close.

How about this, if I do keep the alarm sensors separate, can I use OH to arm/disarm the alarm system? Is that a pretty standard automation I can do with OH?


Not sure if this is what you want to achieve, but most of advanced alarm systems has a way to integrate with other systems. Those available in OH that I am aware of are DSC and Satel.

Or you would like to wire sensors directly somehow to OH? If yes, I don’t think it makes sense. Alarm systems are built to be secure and resilient and have good power backup at least for 24h.

If you would like just monitor sensors wired to alarm system, for sure you can do this with Satel. Not sure about DCS.

Moreover with Satel Alarm you can switch outputs (relays), check alarms, clear alarms, clear troubles, read troubles, arm/disarm partitions, etc. It is pretty flexible but I am not sure if is available in your country.

Thanks @druciak… I believe it makes sense to just have an alarm system that OH2 can control/monitor and not try to use the sensors to trigger OH2 automations. I’ll use separate sensors for that. I need to do a little research on DSC and see what they offer. Appreciate it!

DSC and Honeywell are popular choices because they both have RS232/Serial interfaces

Why? It really depends on what you’re going to control. Turning on a light in some room when you receive OPEN signal from sensor mounted on door to this room (and wired to alarm system) definitely makes sense. And there are many other examples of integrating alarm system’s sensors to automate things in OH. Including setting heating to a lower temp. when you arm you alarm system.

In my case openHAB IS my security system, so the only difference between what a PIR or door sensor does is in my rules.

If the external alarm system is capable of either pushing the sensor’s states (beste case!) or even if you can pull them (second best), you could use that one in rules.
My caveat is always, that vital systems do deserve dedicated (and certified) devices and appliances. OpenHAB can be the means to automate things, you would do otherwise manually. That’s what home automation systems are designed for.
So to pick up druciak’s use case of using the arming of your alarm system for putting your heating to standby state is viable and something opeHAB is really best for - to bridge the gap between otherwise seperate systems.

This is actually what I was hoping to do originally. Ideally if I could find an alarm system that would allow me to piggy back and use its sensors in OpenHAB as you described above would be great.